The goal of this research is to increase the clinical utility of the CEA assay for diagnosis and monitoring of malignant disease. The basic approach being used is to define CEA chemically and to identify distinctive portions of the molecule against which antisera can be prepared. Since research in our laboratory strongly suggests that the antigenic activity of the CEA molecule resides in the protein chain, particular attention will be given to determining the structure of this chain and the synthesis of portions of it for use in immunizations to provoke the synthesis of specific antibody.